1. The field of art to which the invention pertains includes the art of measuring and testing as applicable to amplifier movements for gauge instruments.
2. Amplifier movements for use with pressure gauges, temperatures gauges or the like are well known and have been used commercially for many years. Typically, such gauges have a condition responsive element such as a bellows, Bourdon tube, bi-metal coil or the like providing a displacement in response to condition changes to which the element is sensitive. In a common construction, the amplifier or "movement" is comprised of leverage and gearing operably responsive to arcuate deflective motion of the element for driving an output shaft supporting a pointer movable relative to a fixed dial plate. The dial registration opposite the pointer position is indicative of the condition state such as pressure or temperature with which the instrument is being operative.
Traditionally, such prior amplifiers or movements include various elements of sturdy construction which are fixed or anchored relative to the motion path of the element. It is usual for the pointer shaft and one or more of the intermediate components to be operated about such an axis. Performance of those gauge constructions are capable of providing high levels of readout accuracy and have therefore been generally regarded as satisfactory. Notwithstanding their general acceptability, they are marketed on a highly competitive basis such that their maufacturing costs largely dictate ultimate consumer price and consequent profit.
Contributing significantly toward those costs are several factors not least of which is the construction mass per se of the components associated with the prior art type stationary movements requiring fixed posts, plates or the like to which the anchored axes components can be secured. In addition, such units are characteristically regarded as complex and difficult to calibrate because of the different adjustment settings, each of which mutually affect each other. It is not unknown for many man hours to be consumed in obtaining final calibration in order to meet the expected operating standards of the instrument. Yet another high cost factor has been the need for a relatively expensive hair spring or the like employed to minimize or overcome slack between components that might otherwise arise to adversely affect operation and accuracy. Moreover, by virtue of their constructions, it has been impractical if not impossible to obtain effective temperature compensation for maintaining instrument accuracy throughout wide temperature ranges to which it is subjected. The latter is generally attributable to utilization of a temperature sensitive link as part of the movement located within the case concealed or otherwise unresponsive to environmental changes occurring elsewhere. Despite recognition of these inherent drawbacks, the prior stationary type movements have continued heretofore to be employed as the industry standard for lack of a suitable alternative. Exemplifying movements of the prior art are those disclosed in U.S. Pat. Nos. 3,214,979; 1,658,840 and 1,584,742.